This is where the Desktop Handset comes in. This simple gadget basically acts as a base and receiver for your iPhone. It will plug into your phones earphone jack, and will charge via USB or a wall outlet, allowing your iPhone to become a desktop handset.
The Desktop Handset has a receiver for you to answer or make calls without having to hold the iPhone up to your ear.
This Desktop Handset costs about $59.95 and if you are interested you can buy it from here.